Skip to contents

Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.

Setup code

To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:

library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)

plotly_widget <- plot_ly(x = diamonds$cut) %>%
  config(displayModeBar = FALSE) %>%
  layout(margin = list(t = 0, b = 0, l = 0, r = 0))

leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
  leaflet(options = .) %>%
  addTiles()

Shiny usage

Cards work equally well in Shiny. In the examples below, replace plotly_widget with plotlyOutput() and leaflet_widget with leafletOutput() to adapt them for Shiny server-rendered plots/maps.

Hello card()

A card() is designed to handle any number of “known” card items (e.g., card_header(), card_body(), etc) as unnamed arguments (i.e., children). As we’ll see shortly, card() also has some useful named arguments (e.g., full_screen, height, etc).

At their core, card() and card items are just an HTML div() with a special Bootstrap class, so you can use Bootstrap’s utility classes to customize things like colors, text, borders, etc.

card(
  card_header(
    class = "bg-dark",
    "A header"
  ),
  card_body(
    markdown("Some text with a [link](https://github.com)")
  )
)
A header

Some text with a link

Implicit card_body()

If you find yourself using card_body() without changing any of its defaults, consider dropping it altogether since any direct children of card() that aren’t “known” card() items, are wrapped together into an implicit card_body() call.1 For example, the code to the right generates HTML that is identical to the previous example:

card(
  card_header(
    class = "bg-dark",
    "A header"
  ),
  markdown("Some text with a [link](https://github.com).")
)
A header

Some text with a link.

Restricting growth

By default, a card()’s size grows to accommodate the size of its contents. Thus, if a card_body() contains a large amount of text, tables, etc., you may want to specify a height or max_height. That said, when laying out multiple cards, it’s likely best not to specify height on the card(), and instead, let the layout determine the height layout_column_wrap().

Although scrolling is convenient for reducing the amount of space required to park lots of content, it can also be a nuisance to the user. To help reduce the need for scrolling, consider pairing scrolling with full_screen = TRUE (which adds an icon to expand the card’s size to the browser window). Notice how, when the card is expanded to full-screen, max_height/height won’t effect the full-screen size of the card.

card(
  max_height = 250,
  full_screen = TRUE,
  card_header(
    "A long, scrolling, description"
  ),
  lorem::ipsum(paragraphs = 3, sentences = 5)
)
A long, scrolling, description

Lorem consequat egestas ac, pretium metus, euismod aliquet eu? Arcu consequat fusce eleifend fermentum proin duis venenatis ante neque. Sociis pellentesque cursus lobortis curae maecenas; nascetur; vestibulum per. Molestie potenti placerat ultrices pretium convallis; malesuada semper nunc nec neque sed at potenti phasellus vivamus vitae lacinia. Taciti sapien curabitur dis tempor iaculis leo etiam mattis?

Consectetur dis nunc dignissim condimentum eleifend dictum aptent. Pretium mollis diam ante enim malesuada. Viverra inceptos scelerisque magnis primis consequat nam nam montes porta. Posuere justo penatibus penatibus, quis congue sollicitudin senectus. Duis aliquet posuere ac posuere dui rutrum maecenas, senectus congue torquent praesent a quam tincidunt in aliquet convallis?

Ipsum lacus nullam, bibendum sodales convallis eleifend, tempus class hendrerit. Orci nostra phasellus cubilia sagittis, quis per, laoreet integer consequat ultricies? Euismod facilisis est a netus aptent tempus; quisque rutrum dictumst lectus? Senectus dui porta cum nunc eros himenaeos, purus class sodales. Na sodales.

Filling outputs

A card()’s default behavior is optimized for facilitating filling layouts. More specifically, if a fill item (e.g., plotly_widget), appears as a direct child of a card_body(), it resizes to fit the card()s specified height. This means, by specifying height = 250 we’ve effectively shrunk the plot’s height from its default of 400 down to about 200 pixels. And, when expanded to full_screen, the plot grows to match the card()’s new size.

card(
  height = 250,
  full_screen = TRUE,
  card_header("A filling plot"),
  card_body(plotly_widget)
)
A filling plot

Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny output bindings (e.g, plotOutput(), imageOutput(), etc) are fill items by default, so this behavior “just works” in those scenarios. And, in some of these situations, it’s helpful to remove card_body()’s padding, which can be done via spacing & alignment utility classes.

card(
  height = 275,
  full_screen = TRUE,
  card_header("A filling map"),
  card_body(
    class = "p-0",
    leaflet_widget
  ),
  card_footer(
    class = "fs-6",
    "Copyright 2023 RStudio, PBC"
  )
)
A filling map

Fill item(s) aren’t limited in how much they grow and shrink, which can be problematic when a card becomes very small. To work around this, consider adding a min_height on the card_body() container. For example, try using the handle on the lower-right portion of this card example to make the card taller/smaller.

This interactive example is a bit contrived in that we’re using CSS resize to demonstrate how to make plots that don’t shrink beyond a certain point, but this concept becomes quite useful when implementing page-level filling layouts (i.e., page_fillable()) with multiple cards.

card(
  height = 300,
  style = "resize:vertical;",
  card_header("Plots that grow but don't shrink"),
  card_body(
    min_height = 250,
    plotly_widget,
    plotly_widget
  )
)
Plots that grow but don't shrink

Troubleshooting fill

As you’ll learn more about in filling layouts, a fill item loses its ability to fill when wrapped in additional UI element that isn’t a fillable container. To fix the situation, use as_fill_carrier() to allow the additional element to carry the potential to fill from the card_body() down to the fill item.

Multiple card_body()

A card() can have multiple card_body()s, which is especially useful for:

  1. Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
  2. Allowing each card_body() to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g., min_height).

For example, when pairing filling output with scrolling content, you may want min_height on the filling output since the scrolling content will force it to shrink:

card(
  height = 375,
  full_screen = TRUE,
  card_header(
    "Filling plot, scrolling description"
  ),
  card_body(
    min_height = 200,
    plotly_widget
  ),
  card_body(
    class = "lead container",
    lorem::ipsum(paragraphs = 10, sentences = 5)
  )
)
Filling plot, scrolling description

Dolor vivamus dapibus vulputate ullamcorper molestie rutrum aenean ullamcorper? Faucibus tempus inceptos morbi quam; aenean sapien lectus porttitor? Euismod euismod mi integer? Sed convallis: ultricies dictumst curabitur augue – accumsan lacus velit mattis morbi pharetra vehicula lobortis! Mus suscipit sapien lacus natoque aliquam pharetra metus interdum aptent; duis ornare nullam.

Amet ad mus massa massa nulla, mi phasellus volutpat at phasellus vestibulum? Urna etiam rutrum pretium cursus sed aliquam luctus; congue eu tempus? Leo convallis mi non ultricies justo donec orci feugiat ultricies. Faucibus ornare sollicitudin magnis litora posuere risus bibendum. Diam eros ornare rhoncus sociosqu; curabitur semper!

Ipsum nec lacus montes massa potenti tempus commodo? Vehicula taciti massa nullam – odio egestas fames metus auctor. Nisl mi imperdiet nam maecenas lacinia nisi nisl in? Vestibulum auctor ullamcorper, sed interdum proin imperdiet eleifend metus. Commodo urna mus morbi nisl ultricies mus, tristique duis egestas accumsan dui placerat himenaeos, sapien sollicitudin senectus.

Elit rutrum pharetra eu non lacus congue. Praesent nostra vivamus bibendum gravida. Class venenatis tempus duis egestas risus dis? Primis porttitor, eros ut aliquet turpis, hac primis etiam dictum. Malesuada libero feugiat, suscipit facilisi nisi, ante commodo nostra per litora aptent ac integer.

Sit accumsan sociis proin metus orci himenaeos rhoncus porta placerat conubia. Dapibus nibh cursus integer litora auctor? Vestibulum dui mus: sollicitudin mi. Mus ad pretium a magna: cras id imperdiet tempor magna est. Lectus mus eget at netus nullam arcu nisl dictumst volutpat augue dignissim vestibulum senectus, phasellus eget at convallis quisque ultrices!

Adipiscing nulla at habitant at ullamcorper bibendum. Sodales turpis at, habitasse tempor tortor cras facilisi. Lectus montes ad turpis proin. Massa montes platea suscipit mollis cubilia venenatis ultricies. Enim nunc morbi ultricies primis inceptos: nec enim arcu lectus convallis fusce sociis faucibus tincidunt: non urna vitae scelerisque rhoncus, taciti montes viverra dis pretium etiam.

Dolor urna aliquam enim facilisis, per montes neque odio euismod. Torquent ad aptent dictum pharetra vivamus sollicitudin ligula nunc integer fames? Etiam litora et quisque diam quisque aptent neque ridiculus turpis ornare. Venenatis aliquam nascetur sociosqu ut consequat arcu neque vestibulum fermentum. Pharetra tortor et cubilia, tincidunt nam eros pellentesque vulputate senectus.

Lorem mus nunc felis laoreet gravida, fringilla nam aenean nullam tempus. Luctus mollis torquent, nisl erat suscipit euismod volutpat? Nisl condimentum quis, felis vehicula litora laoreet ultricies mi senectus. At nascetur feugiat dapibus ut dapibus eget natoque nibh luctus. Dapibus!

Elit suscipit taciti luctus arcu cum, vel faucibus netus nullam! Non per tortor accumsan consequat parturient senectus purus ad habitasse. Sem quam netus sem, eros potenti curae curae curae rutrum velit habitant condimentum. Felis fringilla nisi, cursus condimentum pulvinar? Fames dictumst integer nostra, sociosqu enim platea quam turpis, pharetra fusce rutrum morbi.

Consectetur dictumst hac scelerisque potenti, torquent dui ac sollicitudin dignissim. Ante fringilla dictumst scelerisque felis dapibus nisi odio lacus, conubia sociis dis faucibus convallis. Sapien blandit turpis dis, tristique libero varius tempor? Facilisi pharetra curabitur diam taciti, fringilla fames. Ad sollicitudin vivamus morbi congue ante sodales euismod tortor cum.

Also, when the content has a fixed size, and should not be allowed to scroll, set fill = FALSE:

card(
  height = 350,
  full_screen = TRUE,
  card_header(
    "Filling plot, short description"
  ),
  plotly_widget,
  card_body(
    fill = FALSE, gap = 0,
    card_title("A subtitle"),
    p(class = "text-muted", "And a caption")
  )
)
Filling plot, short description
A subtitle

And a caption

Multiple columns

As you’ll learn in column-based layouts, layout_column_wrap() is great for multi-column layouts that are responsive and accommodate for filling output. Here we have an equal-width 2-column layout using width = 1/2, but it’s also possible to have varying column widths.

card(
  height = 350,
  full_screen = TRUE,
  card_header("A multi-column filling layout"),
  card_body(
    min_height = 200,
    layout_column_wrap(
      width = 1/2,
      plotOutput("p1"),
      plotOutput("p2")
    )
  ),
  lorem::ipsum(paragraphs = 3, sentences = 5)
)
A multi-column filling layout

Lorem erat quis aenean ut vulputate penatibus facilisi imperdiet fermentum vestibulum! Aenean rutrum sociosqu montes nisl – augue per quis penatibus velit proin. Morbi vivamus erat in aliquet gravida? Taciti lectus primis quisque etiam vestibulum ut, condimentum pharetra suspendisse non ligula. Rutrum?

Consectetur interdum, curae nunc nascetur a est justo, praesent parturient semper volutpat phasellus primis. Senectus sapien diam nam iaculis – erat facilisi class taciti. Aliquet sapien suscipit faucibus volutpat nulla platea viverra pharetra vitae, sapien diam interdum. Senectus maecenas lacus dapibus, sodales inceptos felis fringilla fermentum. Dapibus dapibus orci urna?

Ipsum mi platea facilisis enim lacinia! Senectus sapien, imperdiet sociosqu ligula nisl litora ornare vestibulum aliquam massa. Aenean montes purus nunc malesuada conubia mattis viverra! Proin sociis aliquam mollis pretium class: tellus risus vehicula justo. Massa tempus cubilia posuere ridiculus natoque varius aenean: aliquet turpis tellus aenean inceptos natoque rutrum placerat potenti ut.

Multiple cards

layout_column_wrap() is especially nice for laying out multiple cards since each card in a particular row will have the same height (by default). Learn more in column-based layouts.

layout_column_wrap(
  width = 1/2,
  height = 300,
  card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
  card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)
A filling plot
A filling map

Multiple tabs

navset_card_tab() and navset_card_pill() make it possible to create cards with multiple tabs or pills. These functions have the same full_screen capabilities as normal card()s as well some other options like title (since there is no natural place for a card_header() to be used). Note that, each nav_panel() object is similar to a card(). That is, if the direct children aren’t already card items (e.g., card_title()), they get implicitly wrapped in a card_body().

library(leaflet)
navset_card_tab(
  height = 450,
  full_screen = TRUE,
  title = "HTML Widgets",
  nav_panel(
    "Plotly",
    card_title("A plotly plot"),
    plotly_widget
  ),
  nav_panel(
    "Leaflet",
    card_title("A leaflet plot"),
    leaflet_widget
  ),
  nav_panel(
    shiny::icon("circle-info"),
    markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
  )
)
HTML Widgets
A plotly plot
A leaflet plot

Learn more about htmlwidgets

As you’ll learn more about in sidebar layouts, layout_sidebar() just works when placed inside in a card(). In this case, if you want fill items (e.g., plotly_widget) to still fill the card like we’ve seen before, you’ll need to set fillable = TRUE in layout_sidebar().

card(
  height = 300,
  full_screen = TRUE,
  card_header("A sidebar layout inside a card"),
  layout_sidebar(
    fillable = TRUE,
    sidebar = sidebar(
      actionButton("btn", "A button")
    ),
    plotly_widget
  )
)
A sidebar layout inside a card

Static images

card_image() makes it easy to embed static (i.e., pre-generated) images into a card. Provide a URL to href to make it clickable. In the case of multiple card_image()s, consider laying them out in multiple cards with layout_column_wrap() to produce a grid of clickable thumbnails.

card(
  height = 300,
  full_screen = TRUE,
  card_image(
    file = "shiny-hex.svg",
    href = "https://github.com/rstudio/shiny"
  ),
  card_body(
    fill = FALSE,
    card_title("Shiny for R"),
    p(
      class = "fw-light text-muted",
      "Brought to you by RStudio."
    )
  )
)
Shiny for R

Brought to you by RStudio.

Flexbox

Both card() and card_body() default to fillable = TRUE (that is, they are CSS flexbox containers), which works wonders for facilitating filling outputs, but it also leads to surprising behavior with inline tags (e.g., actionButton(), span(), strings, etc). Specifically, each inline tag is placed on a new line, but in a “normal” layout flow (fillable = FALSE), inline tags render inline.

card(
  card_body(
    fillable = TRUE,
    "Here's some", tags$i("inline"), "text",
    actionButton("btn1", "A button")
  ),
  card_body(
    fillable = FALSE,
    "Here's some", tags$i("inline"), "text",
    actionButton("btn2", "A button")
  )
)
Here's some inline text
Here's some inline text

That said, sometimes working in a flexbox layout is quite useful, even when working with inline tags. Here we leverage flexbox’s gap property to control the spacing between a plot, a (full-width) button, and paragraph. Note that, by using markdown() for the paragraph, it wraps the results in a <p> tag, which means the contents of the paragraph are not longer subject to flexbox layout. If we wanted, we could do something similar to render the actionButton() inline by wrapping it in a div().

card(
  height = 325, full_screen = TRUE,
  card_header("A plot with an action links"),
  card_body(
    class = "gap-2 container",
    plotly_widget,
    actionButton(
      "go_btn", "Action button",
      class = "btn-primary rounded-0"
    ),
    markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
  )
)
A plot with an action links

Here's a simple hyperlink.

In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.

card(
  height = 300, full_screen = TRUE,
  card_header(
    class = "d-flex justify-content-between",
    "Centered plot",
    checkboxInput("check", " Check me", TRUE)
  ),
  card_body(
    class = "align-items-center",
    plotOutput("id", width = "75%")
  )
)
Centered plot

Shiny

Since this article is statically rendered, the examples here use statically rendered content/widgets, but the same card() functionality works for dynamically rendered content via Shiny (e.g., plotOutput(), plotlyOutput(), etc).

An additional benefit that comes with using shiny is the ability to use getCurrentOutputInfo() to render new/different content when the output container becomes large enough, which is particularly useful with card(full_screen = T, ...). For example, you may want additional captions/labels when a plot is large, additional controls on a table, etc (see the value boxes article for a clever use of this).

# UI logic
ui <- page_fluid(
  card(
    max_height = 200,
    full_screen = TRUE,
    card_header("A dynamically rendered plot"),
    plotOutput("plot_id")
  )
)

# Server logic
server <- function(input, output, session) {
  output$plot_id <- renderPlot({
    info <- getCurrentOutputInfo()
    if (info$height() > 600) {
      # code for "large" plot
    } else {
      # code for "small" plot
    }
  })
}

shinyApp(ui, server)

Appendix

The following CSS is used to give plotOutput() a background color; it’s necessary here because this documentation page is not actually hooked up to a Shiny app, so we can’t show a real plot.

.shiny-plot-output {
  background-color: #216B7288;
  height: 400px;
  width: 100%;
}